Viewpoint--USB 3.0: Not just for wired apps

The need to deliver faster, power efficient data transfers on every device is more evident than ever. NetGear, for example, recently demonstrated a commercially available Wi-Fi-AC router and adapter running at 1.2 gigabits per second (Gbps). Given that consumers want to move terabytes of video and photos through their homes and into the cloud., minimizing power consumption is the No. 1 design challenge.

USB 2.0 remains the standard for wired data transfer, but designers implementing Wi-Fi and Long Term Evolution (LTE) systems-on-chip (SoCs) are switching from USB 2.0 to USB 3.0. Why? Because USB 2.0 effective throughputs are only about 0.35 Gbps and USB 2.0 consumes more power per megabyte than USB 3.0.

“Fine,” you say. “Designers should use USB 3.0 for physical ports, but my product sends and receives data wirelessly. What do I need it for?”

If your product will hit the market in 2014 and 2015, pay attention:

Wi-Fi and LTE speeds will exceed 1 Gbps, which is 3 to 5x faster than USB 2.0

USB 3.0 enables lower power consumption than standard USB 2.0 PHYs by using an M-PHY with SuperSpeed Interchip (SSIC)

Wi-Fi at super speeds

Designing USB 3.0 into Wi-Fi/LTE products help designers keep up with increasing wireless speeds. The current generation of Wi-Fi is called Wi-Fi-N. With a single antenna, WiFi-N runs up to 0.15 Gbps. With multiple-in multiple-out antennas, Wi-Fi-N runs faster. Two antennas for receive and two for transmit (2x2) offer twice the speed (0.30 Gbps), and the 3x3 antennas offer up to 0.45 Gbps. This is much faster than USB 2.0’s effective 0.35 Gbps. USB 3.0 is needed to take advantage of Wi-Fi-N throughput.

Greater leaps in speed are being made in the fifth generation of WiFi, called WiFi-AC. WiFi-AC operates at 1 Gbps or higher, of which USB 2.0 can only support 30%. Only products with USB 3.0 will be able to take advantage of these full Wi-Fi-AC product speeds.

In addition to the upcoming Wi-Fi-AC products, LTE Advanced (LTE-A) modems will begin shipping in 2014 or earlier. LTE-A will start at 0.50 Gbps, allowing mobile users to share and synchronize data, music, pictures and videos in the cloud.

The in-home cloud

USB 3.0 will help enable consumers to store all their photos, videos, music and other data in hard drives attached to a router/gateway, and to access them wirelessly in an in-home, personal cloud. USB 3.0 will be in the WiFi-AC routers that create Wi-Fi networks. These routers will have one or more USB 3.0 host ports allowing consumers to connect USB 3.0 hard drives to a network, as shown in Figure 2, and create their own in-home Internet clouds for storage without a dedicated server or PC. Using Wi-Fi-AC allows data transfers at Gbps speeds between a notebook/tablet/phone and personal cloud.

Reduce power consumption with SSIC and USB 3.0

Key enablers of USB 3.0 in WiFi and LTE products are high-bandwidth, low-power M-PHY interfaces that support the SuperSpeed Interchip (SSIC) specification. USB 3.0 is used outside the box between a host and device. SSIC brings USB from outside of the box to the inside.

To reduce power consumption, mobile apps processors that run smart phones use a USB 3.0 host controller with an SSIC interface. The SSIC pins on the apps processor chip connect to the SSIC pins on the USB 3.0 device controller on an LTE modem chip. SSIC delivers USB 3.0 data speeds between chips to match the speed of the wireless protocols. This also reduces power consumption to one-fifth of the power of USB 3.0.

Because it enables reuse of existing software drivers, future Wi-Fi chips and LTE chips will use SSIC to save both effort and power.

Conclusion

Designers working on consumer electronics products scheduled for release in 2014 and 2015 should keep in mind the increasing Wi-Fi and LTE speeds, consumer demand for faster data access, and the need for longer battery life when selecting an interface standard. With higher throughput and lower power, USB 3.0 is an ideal choice.

There are IP solutions available that make it easier to design USB 3.0 into Wi-Fi/LTE and other products., such as DesignWare USB 3.0 controller and DesignWare MIPI M-PHY that support multiple gears and high-speed interfaces, including SSIC.

About the Author

Eric Huang is a Sr. Product Marketing Manager, Synopsys. Eric worked on USB at the beginning in 1995 with the world's first BIOS that supported USB keyboards and mice while at Award Software. After a departure into embedded systems software for real-time operating systems, Eric returned to USB cores and software at inSilicon, the leading supplier of USB IP in the world. inSilicon was acquired by Synopsys in 2002. Eric served as Chairman of the USB On-The-Go Working Group for the USB Implementers Forum from 2004-2006.

Stephen
What if slew rate and clock speed could be controlled and only run at max when the speed is really needed and no interference issues are present? Only run as fast and steep as needed for device service needded. Also can a better USB cable help this?

Careful of USB3.0 RF noise.
Intel released a white paper in April this year titled USB 3.0* Radio Frequency
Interference Impact on 2.4 GHz
Wireless Devices. This outlines the problems that can be created for WiFi through the use of USB3.0. These warnings also apply to other wireless (Cellular) frequencies. If we are not careful we will kill the radio pipe in the name of widening the wired one

In terms of bandwidth, USB3.0 is limited when compared to the PCIe and its upcoming mobile version(s). In terms of power consumption, USB3.0 is not as capable as MIPI-HSI. In terms of protocol overhead, USB3.0 is heavier than PCIe3.0 and beyond. For any SoC or platform to include the various flavors of 802.11, going through USB3.0 simply adds another layer of latency and dies size for NO gain at all. In particular, the argument of LTE is wrong because, as a network function, IP packetization is intrinsic, what a waste if protocol translation like IP-USB--connection--USB-IP is added! USB1.x met its objective, for all low cost peripherals. USB2.0 serves certain applications well but add the unnecessary cost. USB3.0 adds yet another cost burden and now also makes it difficult for further integration. The latter is because nobody dares to take the route to implement the pure LVDS electrical and drop the backward compatibility. Wake up, don't keep on putting bandage on a tired interface because this aligns with the business line of the corporates as well as personal performance within the company. There are other serial interfaces which have headrooms, protocol benefit than USB3.0 for the intended applications!